1. Field of the Invention
The present invention generally relates to a semiconductor integrated circuit device and a fabrication method thereof, and more particularly to a semiconductor integrated circuit device that includes a semiconductor element formed on a support substrate comprising a semiconductor substrate or a silicon on insulator (SOI) substrate and a multi-layer wiring structure formed in an insulator film of the support substrate and a standard cell type fabrication method thereof that includes the steps of modularizing a circuit, which includes a plurality of semiconductor elements, for each function thereof, maintaining each function module as a standard cell in a library and arranging a plurality of standard cells.
2. Description of the Related Art
In a semiconductor integrated circuit device (which may be referred to as a chip hereinafter) that includes a MOS (Metal Oxide Semiconductor) transistor, factors such as chip miniaturization in a fabrication process, the increasing number of devices accommodated on the chip, and enhancement of the operational speed of the chip cause deterioration of the devices and the wiring on the chip, and performance degradation of the devices due to heat generation of the devices.
In general, a heat release mechanism of a package in an IC (Integrated Circuit) assembly is used to address the heat generation of a chip. According to the heat release mechanism, the heat is released by bringing the surface opposite to the semiconductor element surface, on which some devices are formed, of a silicon substrate (semiconductor substrate) into contact with the heat release mechanism.
In addition, the chip is designed to overcome the heat generation of the chip. For instance, the power consumption is reduced by dividing internal functions of the chip and activating a portion thereof so as to prevent the heat generation of the entire chip. Furthermore, a layout of the chip may be improved by adopting a standard cell type cell wiring arrangement. According to this method, each cell has a parameter for power consumption, and a power-consuming cell such as a clock driver, is distributed by using software means such as a cell wiring arrangement tool so as to distribute a heat generation area that causes heat locally on the chip.
Japanese Patent No. 2971464 discloses a method of arranging cells in a chip. In this method, a virtual temperature parameter is included in a standard cell library, and the cells are arranged through adjustment of the virtual temperature and a cost value.
Japanese Patent No. 2798048 discloses a method of adjusting a temperature distribution in a chip by disposing a cell, of which activation rate is higher, on the periphery of the chip.
Also, a MOS transistor having an SOI structure is used to address a problem regarding a MOS transistor channel capacity entailed in miniaturization in a fabrication process. There are three types of SOI structures. FIGS. 1A through 1D are cross-sectional views of a conventional MOS transistor and the three conventional types of a MOS transistor having the SOI structure.
Referring to FIG. 1A, the conventional MOS transistor includes two source regions or two drain regions 9, which are formed to have an interval, on the surface of a silicon substrate 1. Additionally, the conventional MOS transistor includes a gate electrode 13 between the source regions or the drain regions 9 on the silicon substrate 1 via a gate oxide film 11.
Referring to FIG. 1B, a fully-depletion type SOI-MOS transistor (hereinafter referred to as a fully-depletion type SOI transistor) is formed on an SOI substrate 7. The SOI substrate 7 includes a buried oxide film 3 formed on the silicon substrate 1 and a single crystal silicon layer 5 formed on the buried oxide film 3. Two source regions or two drain regions are formed at an interval on the single crystal silicon layer 5. A gate electrode 13 is formed between the two source regions or the two drain regions 9 on the single crystal silicon layer 5 via the gate oxide film 11. In the fully depletion type SOI transistor, the single crystal layer 5 under the channel region is fully depleted.
Referring to FIG. 1C, a partially-depletion type SOI-MOS transistor (hereinafter referred to as a partially-depletion type SOI transistor) is formed on the SOI substrate 7. Two source regions or two drain regions 9 are formed at an interval on the single crystal silicon layer 5. A gate electrode 13 is formed between the two source regions or the two drain regions 9 on the single crystal silicon layer 5 via the gate oxide film 11. The partially-depletion type SOI transistor includes the single crystal silicon layer 5 of a greater film thickness than the fully-depletion type SOI transistor. Also, the partially-depletion type SOI transistor has a non-depleted region at the bottom part of the single crystal silicon layer 5.
Referring to FIG. 1D, a SON (Silicon On Nothing)-MOS transistor (hereinafter referred to as a SON transistor) is formed on the silicon substrate 1 in which a vacancy or a buried oxide film 14 is formed beneath the channel region on the surface. Two source regions or two drain regions 9 are formed to sandwich the channel region above the vacancy or the buried oxide film 14 on the silicon substrate 1. A gate electrode 13 is formed between the two source regions or the two drain regions 9 on the single crystal silicon layer 5 via the gate oxide film 11.
In the SOI MOS transistor and the SON transistor, the channel layer is thin and it is difficult to conduct heat to the silicon substrate due to an insulator. Especially, the fully-depletion type SOI transistor has a self-heating problem due to heat generation of the gate electrode.
Japanese Patent No. 3128931 discloses a simulation method for a semiconductor device. In this simulation method, heat generation due to an SOI device is taken into account, and a temperature variation due to the self heating of the SOI device itself and the mobility due to the temperature variation are calculated. The operation of the SOI device is simulated by using the varied mobility.
The disclosed conventional methods are not intended to prevent a temperature increase of a semiconductor integrated circuit device due to heat generation of a semiconductor element.